Fix issue with ABC-derived classes having their members ignored

ABC-derived classes (i.e. those deriving from the `abc` and `collections.abc` modules) now include their members (as defined in `__dict__`) in generated `autosummary` RST. `__slots__` may still be used to override `__dict__`, but if an ABC-derived class has empty slots, its `__dict__` will be used instead.

Fixes #52

sphinx_automodapi/automodsumm.py

@@ -83,6 +83,7 @@ class members that are inherited from a base class. This value can be
 .. _sphinx.ext.inheritance_diagram: http://sphinx-doc.org/latest/ext/inheritance.html
 """
 
+import abc
 import inspect
 import os
 import re
@@ -551,7 +552,17 @@ def get_members_class(obj, typ, include_public=[],
                 if include_base:
                     names = dir(obj)
                 else:
-                    if hasattr(obj, '__slots__'):
+                    # Classes deriving from an ABC using the `abc` module will
+                    # have empty `__slots__`, unless other slots were declared
+                    # along the inheritance chain. If the ABC-derived class has
+                    # empty slots, we'll use the class `__dict__` instead.
+                    declares_slots = (
+                        hasattr(obj, '__slots__') and
+                        not (type(obj) is abc.ABCMeta and
+                             len(obj.__slots__) == 0)
+                    )
+
+                    if declares_slots:
                         names = tuple(getattr(obj, '__slots__'))
                     else:
                         names = getattr(obj, '__dict__').keys()

sphinx_automodapi/tests/cases/abstract_classes/README.md

@@ -0,0 +1,2 @@
+This example is to make sure that classes derived from the `abc` module will
+have their members listed (https://github.com/astropy/sphinx-automodapi/issues/52).

sphinx_automodapi/tests/cases/abstract_classes/input/index.rst

@@ -0,0 +1 @@
+.. automodapi:: sphinx_automodapi.tests.example_module.abstract_classes

sphinx_automodapi/tests/cases/abstract_classes/output/api/sphinx_automodapi.tests.example_module.abstract_classes.SequenceSubclass.rst

@@ -0,0 +1,27 @@
+SequenceSubclass
+================
+
+.. currentmodule:: sphinx_automodapi.tests.example_module.abstract_classes
+
+.. autoclass:: SequenceSubclass
+   :show-inheritance:
+
+   .. rubric:: Attributes Summary
+
+   .. autosummary::
+
+      ~SequenceSubclass.my_property
+
+   .. rubric:: Methods Summary
+
+   .. autosummary::
+
+      ~SequenceSubclass.my_method
+
+   .. rubric:: Attributes Documentation
+
+   .. autoattribute:: my_property
+
+   .. rubric:: Methods Documentation
+
+   .. automethod:: my_method

sphinx_automodapi/tests/cases/abstract_classes/output/index.rst.automodapi

@@ -0,0 +1,19 @@
+
+sphinx_automodapi.tests.example_module.abstract_classes Module
+--------------------------------------------------------------
+
+.. automodule:: sphinx_automodapi.tests.example_module.abstract_classes
+
+Classes
+^^^^^^^
+
+.. automodsumm:: sphinx_automodapi.tests.example_module.abstract_classes
+    :classes-only:
+    :toctree: api
+
+Class Inheritance Diagram
+^^^^^^^^^^^^^^^^^^^^^^^^^
+
+.. automod-diagram:: sphinx_automodapi.tests.example_module.abstract_classes
+    :private-bases:
+    :parts: 1

sphinx_automodapi/tests/cases/abstract_classes/output/index.rst.automodsumm

@@ -0,0 +1,6 @@
+.. currentmodule:: sphinx_automodapi.tests.example_module.abstract_classes
+
+.. autosummary::
+    :toctree: api
+
+    SequenceSubclass

sphinx_automodapi/tests/example_module/abstract_classes.py

@@ -0,0 +1,37 @@
+import collections.abc
+
+__all__ = ['SequenceSubclass']
+
+
+class SequenceSubclass(collections.abc.Sequence):
+    """
+    Inherits from an ABC.
+    """
+
+    def __init__(self):
+        self._items = []
+
+    def __len__(self):
+        """
+        Must be defined for the collections.abc.Sequence base class.
+        """
+        return len(self._items)
+
+    def __getitem__(self, key):
+        """
+        Must be defined for the collections.abc.Sequence base class.
+        """
+        return self._items[key]
+
+    def my_method(self, parameter):
+        """
+        An example method.
+        """
+        pass
+
+    @property
+    def my_property(self):
+        """
+        An example property.
+        """
+        return 42